The present invention relates to a new and improved construction of bearing arrangement for rotary or rotating machines, especially for the shafts of multi-stage turbines, comprising at least one support or journal bearing and one thrust bearing.
Depending upon the operating state of the rotary machine, i.e. during start-up, under load, during idle running or during shutdown or even during standstill there arise in the case of turbomachines elongations in axial direction. These axial elongations or expansions of the shaft and housing can be of different magnitude. The greater the length of such type turbosets and the greater the temperature gradient during load changes that much greater are also the differences in the lengthwise expansion arising between the shaft and housing. In order to compensate for such type expansion differences it is possible to appropriately increase the axial play which, however, leads to losses in efficiency.
So that the axial play can be maintained as small as possible it has already been proposed to connect the thrust bearing housing with the turbine housing, so that there can be compensated in this manner the different lengthwise expansions arising between the shaft and the housing.
However, such constructions can only be utilised to a limited extent and up to a predetermined turbine size, since otherwise the forces applied to the housing of the thrust bearing become so great that they can lead to lifting and/or blocking of the housing which, in turn, results in damage to the equipment.
Additionally, there are known to the art, for instance from French Pat. No. 899,221, designs wherein the thrust bearing housing is fixedly connected with the foundation. With this construction there are employed separate bearing housings for the support bearing and the thrust bearing.
With such type bearing arrangements the entire length of the shaft line becomes larger and there prevails a greater yieldability of the shafts. This in turn can lead to undesirable scraping of the blading or the shaft seals, and thus, results in noisy running of the turbine.